The present invention concerns aircraft landing gear. More particularly, but not exclusively, this invention concerns multi-wheel landing gears comprising at least one steerable axle. The invention also concerns a locking mechanism for a multi-wheel landing gear bogie including a steerable axle.
Multi-wheel landing gears are often used on large aircraft, for example the Airbus A380. The multi-wheel landing gears are used to support the large loads exerted on the landing gears by the aircraft when taxiing, at take-off, and landing. In order to prevent excess tyre wear caused by tyre scrubbing during taxiing, the multi-wheel landing gear may include at least one pair of wheels mounted on a steerable axle. When not taxiing, and during take-off and landing, it is necessary to lock the steerable axle in the straight ahead position. An example of such a locking system is disclosed in US2010/0078517. US2010/0078517 discloses a spring loaded, wedge shaped, locking mechanism that is arranged to engage with a receiving portion formed in the steerable axle.
FIGS. 1 and 2 show a landing gear arrangement according to the prior art. As can be seen, the steerable axle 10 is pivotally mounted to the landing gear bogie 12. The steerable axle 10 is steerable by an actuator 14 which may extend and retract in order to change the orientation of the steerable axle. The landing gear arrangement includes a locking mechanism that comprises a wedge-shaped locking member 16 that is pivotally mounted to the landing gear bogie 12. The wedge-shaped locking member 16 is arranged to be received by a receiving portion 18 of the steerable axle 10 in order to lock the steerable axle 10 in a ‘straight ahead’ position for taxi, take off, and landing. The wedge-shaped locking member is secured in the locking position by two springs 20 that act to pull the wedge-shaped locking member into the receiving portion. An actuator 22 is arranged to act against the springs 20 in order to move the wedge-shaped locking member from being received within the receiving portion 18, such that the steerable axle 10 is unlocked and pivotal movement, away from the straight ahead position, is allowed.
However, such an arrangement is reliant on the strength of the springs to maintain the steerable axle in a lock configuration, and as the springs contract into the locked position, the force they exert on the locking member decreases. Additionally, if the locking member is not precisely lined up with the receiving portion when attempting to lock the steerable axle, the friction created between the locking member and the receiving section may be too great for the springs acting on the locking member to overcome, such that the steering axle is not fully locked. If the steering axle is not fully locked, the aircraft is not able to take off until the problem is fixed, which may cause delays to the aircraft departure time or the grounding of the aircraft.
The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved landing gear mechanism.